(a) Field of the Invention
(b) Description of the Related Art
The present invention relates to estimating a received signal strength indicator (RSSI), and more particularly relates to a simply realized RSSI estimating apparatus that estimates RSSI and a method thereof, and a recording medium storing a program that realizes the method.
In recent years, various mobile appliances and wireless networks have been developed to offer mobile networking and computing activities to users.
The most important role in wireless communication is to support mobility of users. In other words, a current channel is maintained for guaranteeing wireless communication services even though a mobile user moves from one place to another. To support mobility in wireless communication, RSSI plays an important role for detecting a level of a signal received at a mobile terminal. The RSSI may be used for various purposes.
FIG. 1 is a block diagram of a conventional RSSI estimation apparatus.
As shown in FIG. 1, the conventional RSSI estimation apparatus includes a receive antenna 10, an I-branch analogue/digital converter (ADC) 20, a Q-branch ADC 30, an I-branch square unit 40, a Q-branch square unit 50, an accumulating and dump unit 60, and an averaging unit 70.
Throughout the specification, “I-branch signal” and “Q-branch signal” respectively represent “in-Phase branch signal” and “Quadrature branch signal.”
The receive antenna 10 receives a radio signal from a base station through a radio channel, and the I-branch and Q-branch ADCs 20 and 30 convert I-branch and Q-branch signals I(t) and Q(t) into the corresponding digital signals Ik and Qk and output the digital signals Ik and Qk.
The I-branch and Q-branch square units 40 and 50 respectively square the digital signals Ik and Qk output from the I-branch and Q-branch ADCs 20 and 30 and output the corresponding power signals.
The accumulating and dump unit 60 receives and gathers the power signals respectively output from the I-branch and Q-branch square units 40 and 50, and accumulates the gathered signals for a given time period.
The averaging unit 70 averages signals accumulated by the accumulating and dump unit 60, and outputs an RSSI estimation signal.
The RSSI obtained by the conventional RSSI estimation apparatus of FIG. 1 may be given by [Math Figure 1].
                    RSSI        =                              1            N                    ⁢                                    ∑                              k                =                0                                            N                -                1                                      ⁢                          (                                                I                  k                  2                                +                                  Q                  k                  2                                            )                                                          [                  Math          ⁢                                          ⁢          Figure          ⁢                                          ⁢          1                ]                            where N denotes the number of samples accumulated by the accumulating and dump unit 60 within a given time period, and k denotes an order of the samples within the given period.        
However, the RSSI estimated by the conventional RSSI estimation only satisfies a function relation with an actual RSSI, and thus we do not know the wattage of the estimated RSSI at a wireless communication terminal, and hardware complexity is increased since the I-branch and Q-branch square units 40 ad 50 require a multiplier for measuring wattage for each sample during a given time period.
Prior arts related to the foregoing ADC are disclosed in U.S. Pat. No. 5,675,339, entitled “A/D REFERENCE LEVEL ADJUSTMENT CIRCUIT TO MAINTAIN OPTIMUM DYNAMIC RANGE AT THE A/D,” and U.S. Pat. No. 3,931,584, entitled “AUTOMATIC GAIN CONTROL.”
The former prior art relates to a method for controlling a reference voltage of an ADC and a circuit thereof, and the method includes a sensor for indicating when outputs of the ADC are at least a desired voltage.
In addition, the method includes a processor responsive to the sensor and connected to a digital-to-analogue converter (DAC), which provides a reference voltage for the ADC. The processor provides signals to the DAC which change the reference voltage when an output voltage of an I- or Q-branch component is higher or lower than the reference voltage. However, the former prior art only proposes a method for providing an accurate reference voltage rather than proposing a method for simply measuring RSSI.
The latter prior art discloses a method for minimizing quantization noise of an ADC, and an automatic gain control (AGC) responsive to an input analogue signal having a significantly varying power level provides an output analogue signal of a substantially constant power level to thereby minimize quantization noise of the ADC. However, this method also does not propose a method for simply and accurately measuring an RSSI.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore, it may contain information that does not form the prior art that is already known in this country to a person or ordinary skill in the art.